package likouJava;

public class 环形链表 {
    public boolean hasCycle(ListNode head) {
        if(head == null || head.next ==null){
            return false;
        }

        //创建快慢指针
        ListNode slow = head;
        ListNode fast = head.next;

        //如果有环，一定会相等
        while (slow != fast){
           if(fast == null || fast.next ==null){
               return false;
           }
           slow = slow.next;
           fast = fast.next.next;
        }
        return true;
    }

}
